Heat exchanger and heat transferring member with symmetrical angle portions

ABSTRACT

A plurality of angle portions  2   c  of the fins on an upstream side and those on a downstream side of an air flow are provided so as to be substantially symmetrical with each other. Due to this, bending forces are continuously exerted on a thin plate-like fin material in a direction where the bending deformation of the fin material is cancelled, during the fin forming process. Accordingly, when the angle portions  2   c  are formed it can be prevented in advance that the fin material  11  is deformed in a state where the repeated deformations of the fin material  11  are accumulated in the same direction.

\CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/802,697 filed on Mar. 17, 2004. This application claims the benefitof JP 2003-331735, filed Sep. 24, 2003 and JP 2003-075792 filed Mar. 19,2003. The disclosures of the above applications are incorporated hereinby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat exchanger and, in particular, toa heat exchanger effectively applied to an air conditioner.

More specifically, it relates to a heat exchanger and a heat transfermember, for improving the heat-exchanging performance thereof byproducing a turbulent air-flow flowing through a heat-exchanging memberthereof, which are preferably applied to, for example, a vehicle.

2. Description of the Related Art

In a conventional heat exchanger, fins have slit pieces, which aresegments of the fins and are arranged in a staggered manner in the airflow direction, and the upstream sides, in the air flow, of the slitpieces are bent at around 90 degrees to form bend portions. Due to thebend portions, the air flow around the fins is disturbed so that thethickness of the temperature boundary layer around the fins is preventedfrom increasing in order to increase the heat transfer coefficientbetween the fins and air (for example, refer to Patent document 1).

Another heat exchanger has a plurality of pin-shaped (needle-shaped)fins arranged in an air flow and, thereby, the heat exchanging abilityof the heat exchanger is improved.

[Patent document 1]

Japanese Unexamined Patent Publication (Kokai) No. 63-83591

In the invention disclosed in Patent document 1, slit pieces are formedby cutting and raising parts of a thin plate-shaped fin and bend portionare formed by bending upward the front ends (font edges) of the slitpieces, at around 90 degrees. In this configuration, the above-mentionedbend portions have disadvantages, in the manufacturing thereof, asdescribed below.

That is, as in the invention disclosed in Patent document 1, all bendportions are formed by bending the front ends of the slit pieces, thebending force in the same direction is continuously exerted on the thinplate-shaped fin material and, therefore, while the bend portions areformed the fin material is deformed in a state where the repeateddeformations of the fin material are accumulated in the same direction,in other words, the fin material is bent in a transverse direction ofthe fin material, that is, the air flow direction.

The slit pieces should be regularly arranged at a constant pitch but, asdescribed above, in the invention disclosed in Patent document 1 the finmaterial is likely to be deformed in a state where the repeateddeformations of the fin material are accumulated in the same direction,that is, the fin material is bent in a transverse direction of the finmaterial, that is, the air flow direction. Therefore, it is difficult toreduce the variation of the pitches between the slit pieces. When thevariation of the pitches between the slit pieces is increased, the heattransfer coefficient between the fins and air is decreased and,therefore, the desired heat exchanging ability of the fins is unlikelyto be obtained.

In a heat exchanger having a plurality of pin-shaped (needles-shaped)fins arranged in the air flow, the weight of the heat exchanger isincreased by arranging the fins, that is, a plurality of pins, and theproductivity of the fins is deteriorated by arranging a plurality ofpins on the heat exchanger. Therefore, it is difficult to realize themass production thereof.

If a plurality of the pins are formed by cutting the areas between twopins, much material to be scrapped, during cutting, is produced and,therefore, the material is not effectively used. As a result, it is alsodifficult to realize the mass production thereof.

SUMMARY OF THE INVENTION

The present invention has been developed with the above-mentionedproblems being taken into consideration and the primary object of thepresent invention is to provide a novel heat exchanger differing fromthe prior art. The secondary objective thereof is to prevent the heatexchanging ability of a heat exchanger from being deteriorated whileimproving the productivity of the fins by realizing simple shapes of thefins.

Other object of the present invention is to provide a heat exchangercomprising a simple fin shape in order to improve the productivity ofthe heat exchanger.

Moreover, another object of the present invention is to improve theheat-exchanging performance of a heat exchanger by utilizing a simplefin shape.

To realize the above-mentioned object, in a first aspect of the presentinvention, a heat exchanger comprises:

tubes (1) in which fluid flows; and

fins (2) which are provided on outer surfaces of the tubes (1) andincrease a heat exchanging area with air flowing around the tubes (1);

wherein the fin (2) has substantially plate-shaped plane portions (2 a)and collision walls (2 c) formed by cutting and raising up parts of theplane portion (2 a) at an angle of substantially 90 degrees; and

wherein groups of a plurality of the collision walls (2 c) are formed soas to be substantially symmetric with each other in an air flowdirection.

Due to this construction, bending forces are continuously exerted on thethin plate-like fin material in the directions in which the bendingdeformation of the thin plate-like material caused by the bending forcesis cancelled when the collision walls (2 c) are formed. Accordingly,when the collision walls (2 c) are formed it can be prevented in advancethat the fin material is deformed in a state where the repeateddeformations of the fin material are accumulated in the same direction,that is, the fin material is bent in a transverse direction of the finmaterial, that is, the air flow direction.

Therefore, a variation in the size of the collision walls (2 c) can bereduced.

As a result, while the heat transfer coefficient between air and thefins (2) is increased by the turbulent flow effect caused by thecollision walls (2 c) and also the heat exchanging efficiency isimproved, the shape of the fins (2) can be simplified so that theproductivity of the fins (2) can be improved.

In a second aspect of the present invention, the collision walls (2 c)and parts of the plane portion (2 a) continuously connected to thecollision walls (2 c) form substantially L sectional shapes, and whereinthe substantially L sectional shapes on an upstream side of an air flowand the substantially L sectional shapes on a downstream side of the airflow are in a substantially symmetric relationship with each other.

In a third aspect of the present invention, a heat exchanger comprisestubes (1) in which a fluid flows, and fins (2) which are provided onouter surfaces of the tubes (1) and increase the heat exchanging areawith air flowing around the tubes (1);

wherein the fin (2) has substantially plate-shaped plane portions (2 a)and collision walls (2 c) formed by cutting and raising up parts of theplane portion (2 a); and

wherein, when a ratio (D/C) between a length (C) of the fin (2)orthogonal to the air flow direction and a length (D) of the collisionwalls (2 c) orthogonal to the air flow direction is assumed to be a slitlength ratio (E), the slit length ratio (E) is set within a range notless than 0.775 and not larger than 0.995.

The present applicant has found that the velocity of the air flowingover the collision walls (2 c) considerably varies in accordance withthe variation of the slit length ratio (E) (see FIGS. 21 to 23 describedbelow). Therefore, in the third aspect of the present invention, bysetting the slit length ratio (E) within the above-mentioned suitablerange, it is possible to increase the velocity of air flowing over thecollision walls (2 c) within a prescribed range around the maximum airflow velocity (see FIG. 21). As a result, the effect of the improvedheat transferring performance of the fin due to the collision walls (2c) can be effectively applied.

In a heat exchanger of a fourth aspect of the present inventionaccording to the third aspect thereof, the slit length ratio (E) is setwithin a range of not less than 0.810 and not larger than 0.980.

Due to this, the heat transferring performance of the fin can be furtherimproved by further increasing the velocity of air flowing over thecollision walls (2 c).

In a heat exchanger of a fifth aspect of the present invention accordingto any one of the first, third and fourth aspects thereof, the collisionwalls (2 c) and slit pieces (2 d) of the plane portion (2 a)continuously connected to the collision walls (2 c) form L-shapedsections, and the L-shaped sections on an upstream side of an air flowand the L-shaped sections on a downstream side of the air flow arearranged substantially symmetrically with each other with respect to avirtual plane perpendicular to the plane portions (2 a).

In this construction, a preferable aspect of the present invention canbe realized by L-shaped sections formed by the collision walls (2 c) andthe slit pieces (2 d) of the plane portion (2 a) continuously connectedto the collision walls (2 c).

In a heat exchanger of a sixth aspect of the present invention accordingto any one of the first to fifth aspects thereof, some of a plurality ofthe collision walls (2 c) arranged on the upstream side of the air floware provided with an angle height (H) higher than that of the othercollision walls (2 c) and all of a plurality of the collision walls (2c) arranged on the downstream side of the air flow are provided with anequal angle height (H).

Due to this, the heat transfer coefficient between air and the fins 2 isincreased by producing a turbulent flow in the upstream side of the airflow, and the increase of the total pressure loss (air flow resistance)can be prevented by preventing an excessive turbulent flow from beingproduced in the downstream side of the air flow.

In a heat exchanger of a seventh aspect of the present inventionaccording to any one of the first to sixth aspects thereof, the angleheight (H) of some of a plurality of the collision walls (2 c) arrangedon the upstream side of the air flow becomes higher toward a downstreamdirection of the air flow, and angle height (h) of some of a pluralityof the collision walls (2 c) arranged on the downstream side of the airflow is lower than that (h) of the collision wall (2 c) arranged on amost downstream side in a plurality of the collision walls (2 c)arranged on the upstream side of the air flow.

Due to this, the heat transfer coefficient between air and the fins 2 isincreased by producing a turbulent flow in the upstream side of the airflow, and the increase of the total pressure loss (air flow resistance)can be prevented by preventing an excessive turbulent flow from beingproduced in the downstream side of the air flow.

In a heat exchanger of an eighth aspect of the present inventionaccording to any one of the first to seventh aspects thereof, the fins(2) are corrugated fins formed in a wave shape.

In a heat exchanger of a ninth aspect of the present invention accordingto any one of the first to seventh aspects thereof, the fins (2) areplate fins formed in a plane shape.

In a heat exchanger of a tenth aspect of the present invention accordingto any one of the first and the third to ninth aspects thereof, aprotrusion (2 i) protruding to an air flow upstream side from an endposition of the tube (1) is formed on the fin (2) and the collisionwalls (2 c) are also formed on the protrusion (2 i).

Due to this, a turbulent flow area with a high heat transfer coefficientat a part of the fin (2) which contacts with the wall surface of thetube (1) can be increased (see FIG. 25A described later) and the heattransferring performance of the fin can be effectively improved.

In a heat exchanger of an eleventh aspect of the present inventionaccording to the tenth aspect thereof, at least two of the collisionwalls (2 c) are preferably formed on the protrusion (2 i).

In a heat exchanger of a twelfth aspect of the present inventionaccording to the tenth or the eleventh aspect thereof, a downstream endin an air flow direction of the fin (2) is arranged not to protrude froma downstream end in the air flow direction of the tube (1).

The increase of air flow resistance due to a downstream side end of thefin (2) protruding in an air flowing direction can be prevented and thetotal performance of the heat exchanger can be effectively ensured.

In a heat transfer member, of a thirteenth aspect of the presentinvention, made of a thin plate member, dipped in fluid and therebysupplying or receiving the heat between it and the fluid; it comprisesangle portions (2 c) cut and raised up from the thin plate member, andplane portions (2 a) having a plurality of heat exchanging portions (2e) comprising slit pieces (2 d) continuously connected to root portionsof the angle portions (2 c); and an angle height (H) of the angleportions (2 c) is not lower than 0.02 mm and is not higher than 0.4 mm,and pitch dimension (P) between the heat exchanging portions (2 e)adjacent each other in a fluid flowing direction is not lower than 0.02mm and is not higher than 0.75 mm.

As a result, as shown in FIGS. 8 and 9 described later, the heatexchanging ability of the fins is prevented from being decreased and, atthe same time, the shapes of the fins (2) can be simplified so that theproductivity of the fins (2) can be improved.

In a heat transfer member, of a fourteenth aspect of the presentinvention, made of a thin plate member, dipped in fluid and therebysupplying or receiving the heat between it and the fluid; it comprisesangle portions (2 c) cut and raised up from the thin plate member, andplane portions (2 a) having a plurality of heat exchanging portions (2e) comprising slit pieces (2 d) continuously connected to root portionsof the angle portions (2 c); and an angle height (H) of the angleportions (2 c) is not lower than 0.06 mm and is not higher than 0.36 mm,and pitch dimension (P) between the heat exchanging portions (2 e)adjacent each other in a fluid flowing direction is not lower than 0.08mm and is not higher than 0.68 mm.

As a result, as shown in FIGS. 8 and 9 described later, the heatexchanging ability of the fins is prevented from being decreased and, atthe same time, the shapes of the fins (2) can be simplified so that theproductivity of the fins (2) can be improved.

In a heat transfer member of a fifteenth aspect of the present inventionaccording to the thirteenth aspect or fourteenth aspect thereof, araised angle (θ) of the angle portions (2C) is not smaller than 40degrees and is not larger than 140 degrees.

In a heat transfer member, of a sixteenth aspect of the presentinvention according to any one of the thirteenth aspect to fifteenthaspect thereof, the angle portions (2 c) are cut and raised up in acurved shape from the thin plate member.

In a heat transfer member of a seventeenth aspect of the presentinvention according to any one of the thirteenth to sixteenth aspectsthereof, a ratio (H/L) between the angle height (H) and dimension (L) ofportions, parallel to the fluid flow direction, of the heat exchangeportions (2 e) is not less than 0.5 and is not more than 2.2.

As a result, as shown in FIG. 12 described later, the heat exchangingability is prevented from being decreased and, at the same time, theshapes of the fins can be simplified so that the productivity of thefins can be improved.

In a heat transfer member of an eighteenth aspect of the presentinvention according to any one of the thirteenth to the eighteenthaspect thereof, a relationship between a sectional shape of the heatexchanging portions (2 e) on an upstream side of a fluid flow and asectional shape of the heat exchanging portions (2 e) on a downstreamside of the fluid flow is arranged substantially symmetrically with eachother.

In a heat transfer member of a nineteenth aspect of the presentinvention according to any one of the thirteenth to the eighteenthaspect thereof, the heat exchange portions (2 e) are formed on the planeportions (2 a) so as to align in a row in the fluid flowing direction.

In a heat transfer member of a twentieth aspect of the present inventionaccording to nineteenth aspect thereof, number of the heat exchangingportions (2 e) is larger than a value B/0.75 when a value (B) is lengthof a portion, parallel to the fluid flowing direction, of the planeportions (2 a) and is expressed in a unit of centimeter.

In a heat transfer member of a twenty first aspect of the presentinvention according to any one of the thirteenth to the twentieth aspectthereof, at least a flat portion (2 f) without the angle portion (2 c)is provided between the heat exchange portions (2 e) adjacent each otherin the fluid flowing direction.

Due to this, the flow resistance of the fluid can be reduced.

In a heat transfer member of a twenty second aspect of the presentinvention according to the twenty first aspect thereof, dimension (B) ofa portion, parallel to a fluid flowing direction, of the plane portions(2 a) is not smaller than 5 mm and is not larger than 25 mm, anddimension (Cn) of a portion, parallel to the fluid flowing direction, ofthe flat portions (2 f) is predetermined and is smaller than 1 mm.

Due to this, the flow resistance of the fluid can be reduced.

In a heat transfer member of a twenty third aspect of the presentinvention according to the twenty first aspect thereof, dimension (B) ofa portion, parallel to a fluid flowing direction, of the plane portions(2 a) is larger than 25 mm and is not larger than 50 mm, and dimension(Cn) of a portion, parallel to the fluid flowing direction, of the flatportions (2 f) is not smaller than 1 mm and is not larger than 20 mm.

Due to this, the flow resistance of the fluid can be reduced.

In a heat transfer member of a twenty fourth aspect of the presentinvention according to any one of the thirteenth to twenty third aspectsthereof, when a ratio (D/C) between a length (C) of a thin plate memberorthogonal to the fluid flow direction and a length (D) of the angleportions (2 c) orthogonal to the fluid flow direction is assumed to be aslit length ratio (E), the slit length ratio (E) is set within a rangenot less than 0.775 and not larger than 0.995.

Due to this, as in the third aspect of the present invention, by settingthe slit length ratio (E) within a suitable range, it is possible toincrease the velocity of air flowing over the angle portions (2 c)within a prescribed range near the maximum air flow velocity. As aresult, the effect of the improved heat transferring performance of thefin due to the angle portions (2 c) can be effectively realized.

In a heat transfer member, of a twenty fifth aspect of the presentinvention, made of a thin plate member, dipped in fluid and therebysupplying or receiving the heat between it and the fluid; it comprises aplane portion (2 a) having a plurality of heat exchanging portions (2 e)which comprises angle portions (2 c) cut and raised up from the thinplate member and slit pieces (2 d) continuously connected to rootportions of the angle portions (2 c); and

when a ratio (D/C) between a length (C) of a thin plate memberorthogonal to the fluid flow direction and a length (D) of the angleportions (2 c) orthogonal to the fluid flow direction is assumed to be aslit length ratio (E), the slit length ratio (E) is set within a rangenot less than 0.775 and not larger than 0.995.

Due to this, as in the twenty fourth aspect of the present invention, bysetting the slit length ratio (E) within a suitable range, it ispossible that the effect of the improved heat transferring performanceof the fin due to the angle portions (2 c) can be effectively realized.

In a heat transfer member of a twenty sixth aspect of the presentinvention according to the twenty fourth or twenty fifth aspect thereof,the slit length ratio (E) is set within a range not less than 0.810 andnot larger than 0.980. Therefore, the velocity of air flowing over theangle portions (2 c) is further increased and the heat transferringperformance of the fin can be further improved.

The term “symmetric” in the first, fifth and eighteenth aspects is usedin such a case where the collision walls (2 c), the L-like sectionalshape including the collision walls (2 c) or the heat exchangingportions (2 e) including the angle portions (2 c) are arranged basicallyin a symmetrical state with respect to the air (fluid) flow direction,but it is also used, as described later in the description of theembodiments, in cases such as a case including a small portion having anunsymmetrical shape and a case in which the number of the collisionwalls (2 c), the angle portions (2 c) or the heat exchanging portions (2e) in the upstream side of the air (fluid) flow is different from thatin the downstream side thereof, in a small amount, or the like.

In other words, the term “symmetric” is not limited to a completelysymmetrical case, but is used to include the substantially symmetricalcase (substantially symmetric) in which the fin material is preventedfrom being concentrated in a certain area, during fin forming.

The symbols in the brackets attached to each means are examples forshowing the correspondence with the specific means described in thelater embodiments.

The present invention may be more fully understood from the descriptionof the preferred embodiments of the invention set forth below, togetherwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a front view of a heat exchanger according to embodiments ofthe present invention.

FIG. 2A is a perspective drawing of major components of a heat exchangeraccording to a first embodiment of the present invention.

FIG. 2B is a sectional view taken along a line A-A in FIG. 2A.

FIG. 3 is an exemplary drawing of a roller forming apparatus.

FIG. 4 is a sectional view showing a fin according to a secondembodiment of the present invention.

FIG. 5 is a perspective drawing of major components of a heat exchangeraccording to a third embodiment of the present invention.

FIG. 6A is a sectional view showing a fin arrangement according to afourth embodiment of the present invention.

FIG. 6B is a sectional view showing another fin arrangement according toa fourth embodiment of the present invention.

FIG. 6C is a sectional view showing another fin arrangement according toa fourth embodiment of the present invention.

FIG. 6D is a sectional view showing another fin arrangement according toa fourth embodiment of the present invention.

FIG. 7 is a sectional view of fins showing the definitions of angleheight H and pitch dimension P between heat exchanging portions 2 e.

FIG. 8 is a graph of a numeral simulation result showing therelationship of the pitch dimension P between the heat exchangingportions 2 e with respect to the heat exchanging performance.

FIG. 9 is a graph of a numeral simulation result showing therelationship of the angle height H with respect to the heat exchangingperformance.

FIG. 10 is a graph of a numeral simulation result using the pitchdimension P between the heat exchanging portions 2 e as a parameter.

FIG. 11 is a graph of a numeral simulation result using the angle heightH of the angle portions 2 c as a parameter.

FIG. 12 is a graph including a summary relationship between the ratio(H/L) and the heat exchanging performance, wherein the ratio (H/L) isspecified by the ratio of the dimension H of a portion, parallel to theair flowing direction, of the heat exchanging portions 2 e with respectto the dimension L of a portion, perpendicular to the direction parallelto the air flowing direction, of the heat exchanging portions 2 e.

FIG. 13A is an exemplary drawing showing an air flow over the angleportions 2 c.

FIG. 13B is an exemplary drawing showing another air flow over the angleportion 2 c.

FIG. 14A is a sectional view of a fin showing an arrangement of angleportions according to a seventh embodiment of the present invention.

FIG. 14B is a sectional view of a fin drawing showing an arrangement ofanother angle portions according to the seventh embodiment of thepresent invention.

FIG. 14C is a sectional view of a fin showing an arrangement of anotherangle portions according to the seventh embodiment of the presentinvention.

FIG. 14D is a sectional view of a fin showing an arrangement of anotherangle portions according to the seventh embodiment of the presentinvention.

FIG. 15A is a sectional view of a fin showing an arrangement of yetanother angle portions according to the seventh embodiment of thepresent invention.

FIG. 15B is a sectional view of a fin showing an arrangement of yetanother angle portions according to the seventh embodiment of thepresent invention.

FIG. 15C is a sectional view of a fin showing an arrangement of yetanother angle portions according to the seventh embodiment of thepresent invention.

FIG. 15D is a sectional view of a fin showing an arrangement of yetanother angle portions according to the seventh embodiment of thepresent invention.

FIG. 16 is a perspective drawing of major components of a heat exchangeraccording to an eighth embodiment of the present invention.

FIG. 17 is a sectional view of a fin of a heat exchanger according to anninth embodiment of the present invention.

FIG. 18 is a sectional view of a fin of a heat exchanger according to atenth embodiment of the present invention.

FIG. 19 is a perspective drawing of major components of a heat exchangeraccording to an eleventh embodiment of the present invention.

FIG. 20 is a sectional view taken along a line A-A in FIG. 19.

FIG. 21 is a graph showing the relationship between the slit lengthratio E and the mean air flow velocity of angle portions, according tothe eleventh embodiment.

FIG. 22 is a plan view of major components for illustrating an effect ofthe eleventh embodiment of the present invention, (a) shows a generalview, and (b) and (c) show enlarged views of Z portion in (a).

FIG. 23A is a graph showing the distribution of the air flow velocity inthe longitudinal direction of the fin.

FIG. 23B is a plan view of major components showing a configurationcorresponding to FIG. 23A in longitudinal direction of the fin of ahorizontal axis thereof.

FIG. 24 is a perspective drawing of major components of a heat exchangeraccording to a twelfth embodiment of the present invention.

FIG. 25 shows, in (a), a plan view of major components of a heatexchanger according to the twelfth embodiment of the present invention,and (b) and (c) show plan views of major components of examples incomparison with the twelfth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

In the present embodiment, a heat exchanger according to the presentinvention is applied to a heat radiator of an air conditioner for avehicle. FIG. 1 is a front view of the heat exchanger, i.e. the heatradiator, according to the present embodiment and FIG. 2A is aperspective drawing showing major components of the heat exchangeraccording to the present embodiment and FIG. 2B is a sectional viewtaken along a line A-A in FIG. 2A. In FIG. 1 an air flows in a verticaldirection of the drawing.

Particularly, the heat radiator is a heat exchanger provided on a highpressure side of a vapor compression type refrigerating apparatus forcooling a refrigerant by dissipating the heat of the refrigerantdischarged from a compressor. When a discharge pressure is lower thanthe critical pressure of the refrigerant, the refrigerant in the heatradiator is condensed and, at the same time, dissipates the heatabsorbed by an evaporator, and when the discharge pressure is not lowerthan the critical pressure of the refrigerant the refrigerant in theheat radiator is not condensed and dissipates the heat absorbed by theevaporator and, as a result, the temperature of the refrigerant isreduced.

In detail, the heat radiator comprises a plurality of tubes 1 throughwhich the refrigerant flows, fins 2 attached on the outer surface of thetube 1 and increasing the heat transfer area exchanging the heat withair so as to facilitate the heat exchange between refrigerant and air,header tanks 3 extending in the direction perpendicular to thelongitudinal direction of the tubes 1 at the both longitudinal ends ofthe tubes 1 and being communicated with each end of tubes 1, inserts 4acting as a reinforcement for a core portion including tubes 1, fins 2and the like, as shown in FIG. 1.

In this embodiment, the tubes 1, fins 2, header tanks 3, and inserts 4are all made of a metal (for example, aluminum alloy) and are joinedeach other by soldering.

By the way, the tube 1 has a flat shape, has a plurality of holes, andis provided with a plurality of refrigerant passages inside, as shown inFIG. 2A, by extruding or withdrawing a metal material, and the fins 2are attached on the flat portions of the tube 1 by soldering.

The fin 2 is a corrugated fin formed as a wave and has bend portions 2 bwhich are bent to connect adjacent plane portions 2 a which havesubstantially flat plate shapes and are arranged side by side. In thisembodiment, the corrugated fins 2 having a wave-like shape are formed byperforming roller forming on a thin metallic plate material. The bendportions 2 b of the fin 2 are brazed to the flat portion (plane portion)of the tube 1.

The plane portion 2 a of the fin 2 is then provided with a plurality ofangle portions 2 c which are formed by raising up parts of the planeportion 2 a at a substantially right angle.

To cut and to raise up parts at substantially 90 degrees means that, inpractice, parts of the plane portion 2 a are cut and raised up atsubstantially 90 degrees with respect to the surface of the planeportion 2 a. The raised angle of the angle portions 2 c may be increasedor decreased by a small degree and, therefore, may be around 90 degrees.

The angle portions 2 c are impinged by air flowing over the surface ofthe fin 2, i.e. the plane portion 2 a, so as to disturb the air flowover the plane portion 2 a. Due to this construction, the heat transfercoefficient between the fin 2 and the air is increased.

Therefore, the angle portions 2 c function as collision walls against anair flow. A flat plate-like portion, connecting to a root portion of theangle portion 2 c, of the plane portion 2 a of the fin 2 is referred asa slip piece 2 d. The slip pieces 2 d and the angle portions 2 c form anL-shaped section.

Concretely, when the plane portion 2 a is divided, in the air flowdirection, into two equal parts, i.e. the upstream side and thedownstream side by the virtual plane L₀, the number of the angleportions 2 c on the upstream side and that on the downstream side aresubstantially same and, at the same time, the angle portions 2 c at theupstream side of the air flow are made by raising up the air-flowdownstream parts of the slit pieces 2 d at substantially 90 degrees andthe angle portions 2 c on the air-flow downstream side are made byraising up the upstream parts of the slit pieces 2 d at substantially 90degrees.

Next, the manufacturing method of the fins 2 will be generally describedbelow.

FIG. 3 is an exemplary drawing of a roller forming device. In thedrawing, a thin plate-like fin material 11 withdrawn from a rollmaterial (un-coiler) 10 is pulled with a specific tension by a tensionmachine 12 which exerts a predetermined tension force on the finmaterial 11.

The tension machine 12 comprises a weight tension section 12 a exertinga constant tension force using gravity on the fin material 11 and aroller tension section 12 d, which includes a roller 12 b rotating inaccordance with the advance of the fin material 11 and a spring means 12c exerting a predetermined tension force on the fin material 11 via theroller 12 b.

The predetermined tension force is exerted on the fin material 11 by thetension machine 12 so that the fin height of each of the fins which arebent and formed into angle shapes by a fin forming machine 13 describedlater is maintained at a constant height.

The fin forming machine 13 bends the fin material 11, on which thepredetermined tension force is exerted by the tension machine 12, toform a plurality of the bend portions 2 b (FIGS. 2A and 2B) and to makethe fin material 11 into a wave shape and, at the same time, forms theangle portions 2 c on the area corresponding to the plane portion 2 a.

The fin forming machine 13 comprises a pair of gear-like forming rollers13 a and cutters which are provided on teeth surfaces of the formingrollers 13 a and form the angle portions 2 c. When the fin material 11passes through a space between the forming rollers 13 a, the finmaterial 11 is bent so as to contact the teeth portions 13 b of theforming rollers 13 a and to be formed into a wave shape and, at the sametime, the angle portions 2 c are formed thereon.

A cutting machine 14 cuts the fin material 11 into a predeterminedlength that the bend portions 2 b in a predetermined number are formedon the fin 2. The fin material 11 cut into the predetermined length issent toward a curing device 16 described later by a transfer device 15.

The distance between the adjacent bent portions 2 b of the corrugatedfin 2 formed in a wave shape by bending is generally denoted as a finpitch Pf. The fin pitch Pf, as shown in FIG. 2B as a sectional view ofthe fin, is twice the distance between the adjacent plane portions 2 a.

In detail, the fin pitch (Pf) of the completed fin 2 (the distancebetween the adjacent bend portions 2 b) is small when the pressure angleof the forming rollers 13 a is increased. The fin pitch (Pf) of thecompleted fin 2 is large when the pressure angle of the forming rollers13 a is decreased. In this case, if the difference between the module ofthe forming rollers 13 a and that of the transfer rollers 15 a is within10%, the fins can be formed without replacing the transfer rollers 15 a.

The curing device 16 cures the undulation of the bend portions 2 b bypressing the bend portions 2 b from the direction substantiallyperpendicular to the ridge direction of the bend portions 2 b. Thecuring device 16 comprises a pair of curing rollers 16 a, 16 bsandwiching the fin material 11 and is rotated dependent on the movementof the fin material 11 when it advances. The curing rollers 16 a, 16 bare arranged so that a line connecting the rotational centers of thecuring rollers 16 a, 16 b is perpendicular to the advancing direction ofthe fin material 11.

A brake device 17 comprises brake surfaces 17 a, 17 b coming intocontact with a plurality of the bending portions 2 b and for generatinga friction force in the opposite direction of the advancing direction ofthe fin material 11. The brake device 17 which is located moredownstream, in the advancing direction of the fin material 11, than thecuring device 16 presses and contracts the fin material 11 bytransferring a force generated by the transfer device 15 and by afriction force generated at the brake surfaces 17 a, 17 b, so that thebend portions 2 b of the fin material 11 come into contact with eachother.

A brake shoe 17 c provided with the brake surface 17 a is rotatablysupported at one end of the brake shoe 17 c and a spring member 17 dacting as a friction force adjusting mechanism is located on the otherend thereof. The friction force generated at the brake surfaces 17 a, 17b is adjusted by adjusting the deflection of the spring member 17 d. Thebrake shoe 17 c and a plate portion 17 e forming the brake surface 17 bare made of an abrasion-proof material, such as a die steel.

Next, the operation of the roller forming device for forming the finsaccording to the present embodiment is described in accordance with thestep order of the process performed in the roller forming device.

The fin material 11 is withdrawn from the material roll 10 (withdrawalprocess), the withdrawn fin material is given with the predeterminedtension force in the advancing direction of the fin material 11 (tensiongenerating process). Then, the bend portions 2 b and the angle portions2 c are formed on the fin material 11 by the fin forming machine 13 (finforming process), and the fin material 11 is cut into the predeterminedlength by the cutting machine 14 (cutting process).

Next, the fin material 11, cut into the predetermined length, istransferred to the curing device 16 by the transfer device 15(transferring process). The bend portions 2 b are then pressed by thecuring device 16 so that the undulation of the fin material 11 is cured(curing process) and, at the same time, the fin material 11 iscontracted by the brake device 17 so that the adjacent bend portions 2 bcome into contact with each other (contracting process).

Further, the fin material 11 having experienced the contracting processis expanded due to the its elasticity and is formed to have thepredetermined fin pitch (Pf). Then inspection processes, such as adimension inspection process, are performed and the forming of thecorrugate fins is terminated.

Next, the effects and functions of the present embodiment will bedescribed below.

In the present embodiment, as groups of a plurality of the angleportions 2 c are provided so as to be substantially symmetric with eachother in the air flow direction, bending forces are continuously exertedon the thin plate-like fin material 11, in a direction where the bendingdeformation of the thin plate-like fin material 11 is cancelled, duringthe fin forming process. Accordingly, when the angle portions 2 c areformed it can be prevented in advance that the fin material 11 isdeformed in a state where the repeated deformations of the fin material11 are accumulated in the same direction, in other words, the finmaterial 11 is bent in a transverse direction of the fin material 11,that is, the air flow direction. Therefore, the variations in theshapes, sizes and the like of the slit pieces 2 d and the angle portions2 c can be reduced.

As a result, while the heat transfer coefficient between air and thefins 2 is increased by the turbulent flow effect caused by the angleportions 2 c and also the heat exchanging efficiency is improved, theshape of the fins 2 can be simplified so that the productivity of thefins 2 can be improved.

According to a study by the present applicant, it is preferable that thethickness of each fin 2 is set to between 0.01 and 0.1 mm, the height hof each angle portion (refer to FIG. 2B) to between 0.1 and 0.5 mm, andthe pitch dimension p between the angle portions 2 c (refer to FIG. 2B)is set to between 1.5 and 5 times the angle height h of the angleportions 2 c. In the present embodiment, the thickness of each fin 2 isset to 0.05 mm, the height h of each angle portion to 0.2 mm, and thepitch dimension p between the angle portions 2 c to 2.5 times the angleheight h of the angle portions.

The angle height H is a height of the angle portion including thethickness of the fin 2, as clearly shown in FIGS. 7, 14 and 15 describedlater.

Second Embodiment

In a second embodiment, as shown in FIG. 4, the angle heights h of aplurality of the angle portions 2 c located on the upstream side of theair flow are gradually varied so as to increase toward the downstreamdirection of the air flow. On the other hand, all the angle heights h ofa plurality of the angle portions 2 c located at the downstream side ofthe air flow are identical, are predetermined, and are lower than thelowest angle height h of the angle portion 2 c located at the mostdownstream side in a plurality of the angle portions 2 c located at theupstream side of the air flow.

Due to this, all the angle heights h of a plurality of the angleportions 2 c located at the upstream side of the air flow are higherthan those of the other angle portions 2 c and, therefore, the heattransfer coefficient between air and the fins 2 is increased byproducing a turbulent flow in the upstream side of the air flow, and theincrease of the total pressure loss (air flow resistance) is preventedby preventing an excessive turbulent flow in the downstream side of theair flow.

Even if the effect of the turbulent flow might be increased byincreasing the height of the angle portions at the downstream side inthe air flow, as the fins 2 on the downstream side cannot effectivelyserve for heat exchanging and the pressure loss (air flow resistance) isincreased, the exchanged heat is decreased.

In the second embodiment, as the angle heights H of a plurality of theangle portions 2 c arranged on the upstream side of the air flow aregradually increased towards the downstream direction of the air flow,the group of the angle portions 2 c arranged on the upstream side of theair flow are not completely symmetrical to the group of the angleportions 2 c arranged on the downstream side of the air flow but bothgroups of the angle portions 2 c have L-shaped sections which are acommon feature and the L-shaped sections of the groups are substantiallysymmetrical. Therefore, the arrangement of the angle portions 2 caccording to the second embodiment has a substantially symmetricalrelationship defined in the present invention.

In the first and second embodiments, the number of the angle portions 2c on the upstream side of the air flow is set to the same (each 9) asthat on the downstream side of the air flow, but even if the numbers aredifferent from each other by small amount, such as one, the relationshipof the both groups of the angle portions 2 c is included in the“substantially symmetrical relationship” defined in the presentinvention.

Third Embodiment

In the first and second embodiments described above, heat exchangerscomprising the corrugated fins 2 formed in a wave shape by bending aredisclosed. On the other hand, in a third embodiment, the presentinvention is applied to a heat exchangers comprising plate-like fins 2formed in plate-like shapes, as shown in FIG. 5.

Fourth Embodiment

In the embodiments described above, one group of the angle portions 2 con the upstream side and the other group of the angle portions 2 c onthe downstream side are symmetrical with each other with respect to thevirtual plane L0. On the other hand, in a fourth embodiment, one groupof the angle portions 2 c on the upstream side of an air flow and theother group of the angle portions 2 c on the downstream side of the airflow are symmetrical with each other with respect to the plate portion 2a, in an example such as shown in FIG. 6A, or groups each of which isformed by pair the angle portions 2 c, which are symmetrical with eachother, are aligned in the air flow direction, in examples as shown inFIGS. 6B and 6C.

Alternatively, in an example as shown in FIG. 6D, the position of eachangle portion 2 c with respect to the slit piece 2 d is opposite to thatin the first embodiment. Any one of the arrangements shown in FIGS. 6A,6B, 6C and 6D and the arrangement of the second embodiment (shown inFIG. 4) may, of course, be combined.

Fifth Embodiment

FIG. 7 shows a sectional view of the fin for illustrating a fifthembodiment and the angle height H of the angle portions 2 c is set to0.02 mm or higher and 0.4 mm or lower and, at the same time, the pitchdimension P between the heat exchanging portions 2 e composed of theangle portions 2 c and the slit pieces 2 d which are continuouslyconnected to the root portions of the angle portions 2 c is set to 0.02mm or larger and 0.75 mm or smaller.

As shown in FIG. 7, the pitch dimension P between the heat exchangingportions 2 e is the dimension representing a distance between theadjacent heat exchanging portions 2 e adjacent in the air flow directionand the angle height H is equal to the dimension of a part, of the heatexchanging portion 2 e, parallel to the direction perpendicular to theair flow direction.

FIG. 8 shows the numerical simulation result representing a relationshipbetween the pitch dimension P of the heat exchanging portions 2 e andthe heat exchanging ability of the fins and FIG. 9 shows the numericalsimulation result representing a relationship between the angle height Hof the angle portions 2 c and the heat exchanging ability. As is clearfrom FIG. 8 and FIG. 9 in the case where the angle height H is set to0.02 mm or higher and 0.4 mm or lower and, at the same time, the pitchdimension P of the heat exchanging portions 2 e is set to 0.02 mm orlarger and 0.75 mm or smaller, the heat exchanging ability is improved.

The heat exchanging ability is determined based on the multiplication ofthe heat transfer coefficient and the heat transfer area. In FIGS. 8 and9, the variations of the ratios of the heat exchanging ability of thefins of the present invention against that of fins of a conventionalheat exchanger, in which a louver is installed and which is used as areference, is indicated in accordance with the variations of the pitchdimension P and the angle height H, respectively.

When the angle height H of the angle portions 2 c or the pitch (pitchdimension) P between the heat exchanging portions 2 e is varied, thepressure loss (air flow resistance) of the air flowing around the fin 2,i.e. the plane portion 2 a, is also varied and therefore in thenumerical simulation, as shown in FIGS. 8 and 9, the heat exchangingability is calculated by varying the angle height H of the angleportions 2 c and the pitch P between the heat exchanging portions 2 e,so that the pressure loss (air flow resistance) becomes substantiallyequal by varying a fin pitch Pf which is twice of the distance betweenthe adjacent plate portions 2 a (see FIGS. 2B and 4), in accordance withthe variation of the height H of the angle portions 2 c or the pitch Pbetween the heat exchanging portions 2 e.

In detail, if the fin pitch is increased, the air flow resistance isreduced, as shown in FIGS. 10 and 11, whereas the number of the planeportions 2 a is decreased, so that the heat transfer (exchanging) areaand the heat transfer coefficient are decreased. In contrast, if the finpitch is decreased, the number of the plane portions 2 a is increased,so that the heat transfer area and the heat transfer coefficient areincreased, whereas the air flow resistance is increased.

FIG. 10 shows the result of the numerical simulation test in which thepitch P between the heat exchanging portions 2 e is used as a parameterand FIG. 11 shows the result of the numerical simulation test in whichthe angle height H of the angle portions 2 c is used as a parameter.

As the angle portions 2 c are cut and raised up from the plane portion 2a, the dimension L (refer to FIG. 7) of a part, of the heat exchangingportion 2 e, parallel to the air flow direction varies in accordancewith the height H of the angle portions 2 c and the pitch P between theheat exchanging portions 2 e.

In this case, the ratio (=H/L) is defined as the ratio of the angleheight H of the angle portions 2 c, i.e. the dimension H of the part, ofthe heat exchanging portion 2 e, parallel to the direction perpendicularto the air flow direction, with respect to the dimension L of the partthereof parallel to the air flow direction. Therefore, based on FIGS. 8and 9, the summarized relationship between the ratio H/L and the heatexchanging ability is shown in FIG. 12.

Therefore, when the ratio (=H/L) of the angle height H of the heatexchanging portions 2 e with respect to the dimension L of the part, ofthe heat exchanging portions 2 e, parallel to the air flow direction isnot smaller than 0.5 and not larger than 2.2, a high heat-exchangingability can be attained.

Sixth Embodiment

In the fifth embodiment, the angle height H of the angle portions 2 cand the pitch P between the heat exchanging portions 2 e are determinedso that the heat exchanging ability equal to or higher than the heatexchanging ability of the fins of the conventional heat exchangerprovided with louvers, can be attained, though actual products vary insize, etc.

Due to this, in the sixth embodiment, as the 20% variation in the heatexchanging ability is taken into consideration, the angle height H ofthe angle portions 2 c is set to 0.06 mm or higher and 0.36 mm or lowerand, at the same time, the pitch P between the heat exchanging portions2 e is set to 0.08 mm or larger and 0.68 mm or smaller.

Seventh Embodiment

In the embodiment described above, when the air flow meanders around theangle portions 2 c (particularly, around the angle portions 2 c in thedownstream side of the air flow) as shown in FIG. 13A, the heatexchanging ability (the heat transfer coefficient) is improved andtherefore the cut and raised angle θ of the angle portions 2 c is notlimited to the substantially 90 degrees and, as shown in FIG. 13B, partsof the plane portion 2 a may be cut and raised up to the extent that theair flow can meander.

Therefore, in the seventh embodiment concretely, the cut and raisedangle θ of the angle portions 2 c can be not smaller than 40 degrees andnot larger than 140 degrees. Therefore, the sectional shape of the heatexchanging portions 2 e is not limited to the L shape and it may have,for example, various sectional shapes as shown in FIGS. 14 A to D andFIGS. 15 A to D.

In this case, the cut and raised angle θ of the angle portions 2 c meansthe angle formed by cutting and raising up the plane portion 2 a fromthe reference state in which the plane portion 2 a is not cut and raisedup.

FIG. 14A shows an example in which the cut and raised angle θ is about40 degrees, FIG. 14B shows an example in which the cut and raised angleθ is about 140 degrees, and FIGS. 14C and 14D show examples in whichwhile the cut and raised angle θ is about 40 degrees, the slit pieces 2d are also bent to be inclined with respect to the plane portion 2 a.

FIG. 15A shows an example in which part of the slit piece 2 d present inthe opposite side of the angle portion 2 c is bent so as to be raised upin the direction similar to the angle portion 2 c. FIG. 15B shows anexample in which the angle portions 2 c are cut and raised so thatsmooth arch-like curved surfaces are formed from the slit pieces 2 d tothe angle portions 2 c. FIG. 15C shows an example in which while smootharch-like curved surfaces are formed from the slit pieces 2 d to theangle portions 2 c, part of the slit piece 2 d present in the oppositeside of the angle portion 2 c is bent into a curved surface in thedirection similar to the angle portion 2 c. FIG. 15D shows an example inwhich the directions of the raised parts of the angle portions 2 c arealternately changed.

Eighth Embodiment

An eighth embodiment relates to the number of the heat exchangingportions 2 e, i.e. the angle portions 2 c.

More particularly, when the dimension B of the part, of the planeportion 2 a, parallel to the air flow direction is expressed incentimeters, the number n of the heat exchanging portions 2 e, as shownin FIG. 16, is set to larger than the value of B/0.75.

That is, the number n (n is a natural number) of the heat exchangingportions 2 e is expressed by the following equation (1).n>(B/0.75)  (1)

Ninth Embodiment

In a ninth embodiment, as shown in FIG. 17, at least a flat portion 2 fon which the angle portion 2 c is not formed is provided between theheat exchanging portions 2 e adjacent to each other in the air flowdirection and, at the same time, the dimension B of the plane portion 2a parallel to the air flow direction is made equal to or larger than 5mm and equal to or smaller than 25 mm. In addition, the dimension Cn ofthe flat portion 2 f parallel to the air flow direction is set to thepredetermined dimension (0.5 mm in this embodiment) which is smallerthan 1 mm.

In this way, it is possible to reduce the air flow resistance.

Tenth Embodiment

In a tenth embodiment, as shown in FIG. 18, a plurality of the flatportions 2 f (three in FIG. 18) on which the angle portion 2 c is notformed is provided between the heat exchanging portions 2 e adjacent toeach other in the air flow direction and, at the same time, thedimension B of the plane portions 2 a parallel to the air flow directionis made larger than 25 mm and smaller than 50 mm. In addition, thedimension Cn of the flat portions 2 f parallel to the air flow directionis set to the predetermined dimension (5 mm in this embodiment) which isnot smaller than 1 mm and not larger than 20 mm.

In this way, it is possible to reduce an air flow resistance.

Eleventh Embodiment

FIGS. 19 to 23 shows an eleventh embodiment. In the eleventh embodiment,as shown in FIG. 19, when assuming that the length of the fin 2orthogonal to the air flow direction is defined as C, the length of theangle portion 2 c orthogonal to the air flow direction is defined as D,and the ratio (D/C) of the length C with respect to the length D isdefined as a slit length ratio E, the slit length ratio E is set withinan optimum range in order to improve the heat-exchanging performance ofthe fin 2.

In this case, the length C of the fin 2 orthogonal to the air flowdirection coincides with the interval length between the adjacent tubes1 as shown in FIG. 22. FIG. 20 is a sectional view along line A-A inFIG. 19.

FIG. 21 shows a graph representing a relationship between the slitlength ratio E and the mean velocity of air flow passing through overthe angle portions 2 c (see FIG. 13) and the graph shows the calculationresult of a numerical simulation performed by the applicant.

The main conditions of the numerical simulation include the pitchdimension P between the adjacent heat-exchanging portions 2 e, shown inFIG. 20, equal to 0.5 mm, the dimension L of the air flow direction ofthe heat-exchanging portions 2 e equal to 0.25 mm, the angle height Hequal to 0.25 mm, the fin pitch of the corrugated fins 2 Pf equal to 2.5mm, and the air velocity in front of the heat exchanger equal to 4 m/s.

In this numerical simulation, the angle (portion) length D is fixed to4.5 mm and the fin length C is varied, so that the variation of the meanvelocity of air flow according to the variation of the slit length ratioE is calculated.

In this stage, the phenomenon in which the mean velocity of the air flowvaries according to the variation of the slit length ratio E isexplained with reference to FIGS. 22 and 23. FIGS. 22(b) and 22(c) areenlarged views of the Z portion in FIG. 22(a), FIG. 22(b) shows an airflow in a case where the slit length ratio E (D/C) is set to 0.69 andFIG. 22(c) shows an air flow in a case where the slit length ratio E(D/C) is set to 0.81.

Non-slit portions 2 g and 2 h are formed on both side surfaces, of theangle portions 2 c, in the plane portion 2 a of the fin 2 and airbypassing the angle portions 2 c flows over the non-slit portions 2 g, 2h in the direction indicated by the arrow G in FIG. 22(a). In this case,FIG. 22(b) shows a state in which the slit length ratio E (D/C) isdecreased to 0.69 by increasing the length F of the non-slit portions 2g, 2 h.

Thus, if the slit length ratio E is decreased, the proportion of a flowrate of air, bypassing the angle portions 2 c and flowing over thenon-slit portions 2 g, 2 h in the direction indicated by the arrow G,with respect to the total air flow is not negligible as shown in FIG.22(b). As a result, when the slit length ratio E is equal to 0.69 theair flow velocity becomes the maximum at the non-slit portions 2 g, 2 hwhich are provided outside the angle portions 2 c in the longitudinaldirection of the angle portions 2 c, as shown by a dotted line in FIG.23A, and, accordingly, the velocity of air flowing over the angleportions 2 c is decreased.

The horizontal axis in FIG. 23A represents a ratio of the positionorthogonal to an air flow direction of fins 2, which is measured fromthe center of the fin 2, with respect to the fin length C. In otherwords, the center of the fin length C is defined as 0 and the lengthsfrom the center 0 to the side end portions of the fin 2 are defined as+1 and −1, respectively. Therefore, the total length C of the fin 2 isdefined as 2, in the horizontal axis of FIG. 23A.

On the other hand, if the slit length ratio E is increased to 0.81 asshown in FIG. 22(c), the length F of the non-slit portions 2 g, 2 h isdecreased, so that air hardly passes over the non-slit portions 2 g, 2h. Thereby, the distribution of the air velocity is made uniform and thevelocity of air passing over the angle portions 2 c can be increased asshown by an alternate long and short line in FIG. 23A.

Further, if the slit length ratio E is increased to around 0.94, thevelocity of air passing over the angle portions 2 c can be furtherincreased as shown by a solid line in FIG. 23A. If the slit length ratioE is increased to approach to “1”, the both ends in a longitudinaldirection of the angle portions 2 c approach to the wall surfaces of thetubes 1 (or the bent portions 2 b of the fin), so that the influence ofthe flow resistance due to the wall surface of the tube 1 (or the bentportions 2 b of the fin 2) is increased so as to decrease the air flowvelocity. Therefore, the mean air velocity of air passing over the angleportions 2 c is decreased.

As there is a relation where the heat transferring performance (heattransfer coefficient at the air side) of the fin 2 is improved inaccordance with the increase of the mean air velocity of the air passingover the angle portions 2 c, by selecting the slit length ratio E withinthe optimum range the heat transferring performance of the fin 2 can beeffectively improved.

In FIG. 21 which shows a relationship between the slit length ratio Eand the mean air velocity of the air passing over the angle portions 2c, the mean air velocity takes the maximum around the slit length ratioE=0.90. Thus, in order to improve the heat transferring performance ofthe fin 2 it is most effective to set the slit length ratio E around0.90. When taking the variation of the slit length ratio E, of actualproducts and the like, into consideration, however, the allowabledegrading range of the heat transferring performance thereof is, inpractice, such that the air flow velocity decrease from the maximum airflow velocity is within the range of substantially 10%.

Therefore, the range of the slit length ratio E is set not less than0.775 and not larger than 0.995. Whereby, the heat transferringperformance of the fin 2 can be effectively improved. If the slit lengthratio E is set not less than 0.810 and not larger than 0.980, the airflow velocity decrease from the maximum air flow velocity is within therange of substantially 6% which is more preferable for the improvementof the heat transferring performance of the fin 2.

Twelfth Embodiment

FIG. 24 shows a twelfth embodiment of the present invention. In thetwelfth embodiment, a protrusion 2 i which protrudes in the upstreamside of an air flow from the position of the tube 1 end is formed on thefin 2 and angle portions 2 c are also continuously formed on theprotrusion 2 i. The above construction is made because of the followingreason.

FIG. 25(b) shows an example in comparison with the twelfth embodiment.In the example, the upstream-side end and the downstream-side end, inthe air flow, of the fin 2 coincide with the upstream-side end and thedownstream-side end, in the air flow, of the tube 1, respectively,likely as the first embodiment etc. Therefore, in the example theprotrusion 2 i of the fin 2 according to the twelfth embodiment is notprovided.

The angle portions 2 c produce a turbulent air flow and improve the heattransferring performance of the fin. However, it appears, according tothe precise study of the applicant through experiment, that even if theangle portions 2 c are formed, a laminar flow area is formed on an inletarea in the upstream of the air flow of the fin 2, as shown in FIG.25(b), and a turbulent flow area, that is, an area with a high heattransfer coefficient, is formed on the downstream side of the laminarflow area.

In the twelfth embodiment the above-mentioned point is focused on sothat the protrusion 2 i which protrudes in the upstream side of an airflow from the position of the tube 1 end is formed on the fin 2 and theangle portions 2 c are continuously formed on the protrusion 2 i.

According to the twelfth embodiment, and also on the protrusion 2 iprotruding in the upstream side of an air flow of the fin 2 a turbulentair flow by the angle portions 2 c begins to be produced, a turbulentair flow area having a high heat transfer coefficient can be shifted tothe more upstream side of an air flow than the example in FIG. 25(b), asshown in FIG. 25(a). Thereby, an area having high heat transfercoefficient and formed on a portion of the fin 2 which contacts with thewall surface of the tube 1 is increased from the area of an example forcomparison in FIG. 25(b) (indicated with the dotted line with arrows inFIG. 25(a)) to the area indicated with the solid line with arrows, inFIG. 25(a), so that it is possible to effectively improve the heattransferring performance of the fin.

According to the applicant's study, the protruding length of theprotrusion 2 i is preferably set to a length in which at least two angleportions 2 c can be formed within the protrusion 2 i, in order toimprove the heat transferring performance of the fin.

In FIG. 25(c) showing another example for comparing with the twelfthembodiment, a protrusion 2 j protruding into the downstream side of anair flow from the position of the end of the tube 1 is formed on the fin2. According to the another example, it is possible to produce aturbulent air flow area having a high heat transfer coefficient on theprotrusion 2 j protruding into the air flow downstream side, so that theturbulent air flow area having a high heat transfer coefficient can beincreased from the area of the example for comparison in FIG. 25(b)(indicated with the dotted line with arrows in FIG. 25(c)) to the areaindicated with the solid line with arrows, in FIG. 25(c).

However, as the protrusion 2 j protruding into the air flow downstreamside is provided away from the wall surfaces of the tubes 1, the heat ofhot fluid inside the tube 1 is difficult to reach the protrusion 2 j. Asa result, according to the another comparison example in FIG. 25(c) theturbulent air flow area having a high heat transfer coefficient due tothe protrusion 2 j protruding into the air flow downstream side cannotbe effectively utilized for the improvement of the heat transferringperformance of the fin.

On the other hand, the formation of the protrusion 2 j causes the airflow resistance to be increased and may cause a trouble which decreasesthe heat radiating performance of a heat exchanger.

Accordingly, an arrangement where the fin 2 does not protrude into themore downstream side of the air flow than the downstream-side end of thetube 1, in other words, an arrangement where the downstream side end inan air flow of fin 2 coincides with that of the tube 1 in an air flowdirection (see FIG. 25(a)), is advantageous in order to ensure asufficient heat radiating performance of a heat exchanger.

In this configuration, the coincidence in the arrangement where thedownstream side end in an air flow of fin 2 coincides with that of thetube 1 means the substantial coincidence which allows a small differencebetween the two ends thereof, due to a variation in assembling or thelike.

Other Embodiments

In the embodiments described above, the heat exchanging portions 2 e,i.e. the angle portions 2 c, are formed so as to be arranged on theplane portion 2 a in a row in the air flow direction. However, thepresent invention is not limited to these embodiments and may have anarrangement in which the number of the rows of the heat exchangingportions 2 e is, for example, equal to two or more than two.

In the embodiments described above, the sectional shape of the heatexchanging portions 2 e at the upstream side in the air flow and thesectional shape of the heat exchanging portions 2 e at the downstreamside in the air flow are substantially symmetric with each other but thepresent invention is not limited to these embodiments.

In the embodiments described above, the number of the angle portions 2 cat the upstream side in the air flow and the number of the angleportions 2 c at the downstream side in the air flow are equal but thepresent invention is not limited to these embodiments.

In the embodiments described above, the present invention is applied toa heat radiator of an air conditioner for a vehicle but the applicationof the present invention is not limited to this and the presentinvention may be applied to equipment such as a heater core of an airconditioner for a vehicle, an evaporator or a condenser of a vaporcompression type refrigerator or a radiator.

In the embodiments described above, the fins 2 are fabricated by theroller forming method but the present invention is not limited and thefins 2 may be fabricated by other methods, such as press forming.

In the embodiments described above, the tubes 1 and the fins 2 areconnected by soldering. However the present invention is not limited andthe tubes 1 and the fins 2 can be connected using a mechanical method byenlarging the diameter of the tubes 1.

While the invention has been described by reference to specificembodiments chosen for the purposes of illustration, it should beapparent that numerous modifications could be made thereto by thoseskilled in the art without departing from the basic concept and scope ofthe invention.

1. A heat exchanger comprising: tubes in which a fluid flows; and finswhich are provided on outer surfaces of the tubes and increase a heatexchanging area with air flowing around the tubes; wherein the fin hassubstantially plate-shaped plane portions and collision walls formed bycutting and raising up parts of the plane portion; and wherein when aratio D/C between a length C of the fin orthogonal to the air flowdirection and a length D of the collision walls orthogonal to the airflow direction is assumed to be a slit length ratio E, the slit lengthratio E is set within a range not less than 0.775 and not larger than0.995.
 2. A heat exchanger, as set forth in claim 1, wherein the slitlength ratio E is set within a range of not less than 0.810 and notlarger than 0.980.
 3. A heat exchanger, as set forth in claim 1; whereinthe collision walls and slit pieces of the plane portion continuouslyconnected to the collision walls form L-shaped sections; and wherein theL-shaped sections on an upstream side of an air flow and the L-shapedsections on a downstream side of the air flow are arranged substantiallysymmetrically with each other with respect to a virtual planeperpendicular to the plane portions.
 4. A heat exchanger, as set forthin claim 1, wherein some of a plurality of the collision walls arrangedon the upstream side of the air flow are provided with an angle height Hhigher than that of the other collision walls and all of a plurality ofthe collision walls arranged on the downstream side of the air flow areprovided with an equal angle height H.
 5. A heat exchanger, as set forthin claim 1; wherein the angle height H of some of a plurality of thecollision walls arranged on the upstream side of the air flow becomeshigher toward a downstream direction of the air flow; and wherein theangle height h of some of a plurality of the collision walls arranged onthe downstream side of the air flow is lower than that h of thecollision wall arranged on a most downstream side in a plurality of thecollision walls arranged on the upstream side of the air flow.
 6. A heatexchanger, as set forth in claim 1, wherein the fins are corrugated finsformed in a wave shape.
 7. A heat exchanger, as set forth in claim 1,wherein the fins are plate fins formed in a plane shape.
 8. A heatexchanger, as set forth in claim 1, wherein a protrusion protruding toan air flow upstream side from an end position of the tube is formed onthe fin and the collision walls are also formed on the protrusion.
 9. Aheat exchanger, as set forth in claim 8, wherein at least two of thecollision walls are also formed on the protrusion.
 10. A heat exchanger,as set forth in claim 8, wherein a downstream end in an air flowdirection of the fin is arranged not to protrude from a downstream endin the air flow direction of the tube.
 11. A heat transfer member madeof a thin plate member, dipped in fluid and thereby supplying orreceiving the heat between it and the fluid; wherein it comprises aplane portion having a plurality of heat exchanging portions whichcomprises angle portions cut and raised up from the thin plate memberand slit pieces continuously connected to root portions of the angleportions; and wherein when the ratio D/C between a length C of a thinplate member orthogonal to the fluid flow direction and a length D ofthe angle portions orthogonal to the fluid flow direction is assumed tobe a slit length ratio E, the slit length ratio E is set within a rangenot less than 0.775 and not larger than 0.995.
 12. A heat transfermember, as set forth in claim 11, wherein the slit length ratio E is setwithin a range not less than 0.810 and not larger than 0.980.